Study Ties Type 1 Diabetes to Faster Brain Aging, Reveals Preserving Sight May Be Key to Slowing Decline

February 19, 2025
Written by: Jacqueline Mitchell

First-of-Its Kind Study Comprehensively Characterized Cognitive Function and Brain Pathology in Aging People with T1D

Boston, MA – Investigators at Joslin Diabetes Center have conducted the first comprehensive clinical characterization of cognitive decline in people with long-duration type 1 diabetes (T1D). Published in JCI Insight, the study helps answer questions about this understudied population and hints that preserving eyesight may help prevent cognitive decline in people with T1D, and possibly beyond. 

“Cognitive dysfunction is recognized as a potential complication associated with diabetes, but studies have mostly focused on type 2 diabetes or younger type 1 populations,” said corresponding author George King, Chief Scientific Officer, Joslin Diabetes Center and Thomas J. Beatson, Jr. Professor of Medicine in the Field of Diabetes, Harvard Medical School.

“Detailed clinical characterization of cognitive dysfunction in a large cohort of people with a long history of living with T1D has been limited given that living longer than 55 years with the disease has only recently become possible,” said co-corresponding author, Hetal Shah Joslin Diabetes Center, and Instructor in Medicine, Harvard Medical School. 

Enter the Medalists: Prior to the discovery and widespread accessibility of insulin, diabetes was a fatal condition. As Joslin’s physician-scientists began to help patients get their condition under control, they began awarding medals to people who had been living with diabetes for decades in 1948. Since 1970, Joslin has awarded medals to more than 7,000 people, known as the Medalists, for living with the condition for 50 years. 

King and colleagues recruited more than 1,000 Medalists with type 1 diabetes to participate in the Medalist Study. Participants had a mean age of 66 years and had been living with T1D an average of 53 years. As one might expect, this long-lived group demonstrated healthy habits—eating and exercising as recommended and keeping their blood pressure, cholesterol and blood sugar well-controlled. 

But when Shah, King and colleagues assessed their cognitive function and conducted brain and retinal imaging, they found the Medalists performed worse than people without diabetes in many categories, including recall and psychomotor control (the suite of abilities involved in driving a car or catching a ball.) Neuroimaging revealed the Medalists had lower total brain volume, equivalent to nine years accelerated aging, the researchers calculated. Yet, Medalists did not have significantly higher vascular abnormalities either on neuroimaging or neuropathology, nor did they have significant Alzheimer’s disease pathology, as previous studies have shown in people with type 2 diabetes.

Retinal imaging revealed that worse cognitive function, lower brain volumes, and diabetic retinopathy—a common complication of diabetes—was linked with the thinning of retinal tissues. The scientists also found that worse visual acuity was associated with worse psychomotor skills, worse recall and reduced brain volume. Together, these findings suggest that maintaining eyesight could be one way to modify the course of cognitive decline in this population.  

“Our findings are very different from those reported for people with type 2 diabetes,” said King. “This link between better visual acuity and the preservation of cognitive function and higher brain volumes is novel and suggests a potential therapeutic approach to prevent cognitive decline in T1D that may even be applicable beyond this population to age-related dementia,” said Shah. 

Co-authors included Hetal S. Shah, Surya Jangolla, Marc Gregory Yu, Rebecca Roque, Amanda Hayes, John Gauthier, Nolan Ziemniak, Elizabeth Viebrantz, I-Hsian Wu, Kyoungmin Park, Ward Fickweiler, Tanvi Chokshi, Atif Adam, Jennifer Sun, Lloyd Paul Aiello and George L. King of Joslin Diabetes Center; Matthew DeSalvo, Yogesh Rathi, Anastasia Haidar, Tashrif Billah, Lipeng Ning and Mel B. Feany of Brigham and Women's Hospital.

This study was supported by funding from the Beatson Foundation, Nunnally Foundation, grants from the National Institutes of Health / National Institute of Diabetes and Digestive Kidney Diseases (grants 3P30DK036836-341 and P30DK036836-37) and Mary Iacocca Fellowships.

The authors declare no conflicts of interest.

About Joslin Diabetes Center

Joslin Diabetes Center is world-renowned for its deep expertise in diabetes treatment and research. Part of Beth Israel Lahey Health, Joslin is dedicated to finding a cure for diabetes and ensuring that people with diabetes live long, healthy lives. We develop and disseminate innovative patient therapies and scientific discoveries throughout the world. Joslin is affiliated with Harvard Medical School and one of only 18 NIH-designated Diabetes Research Centers in the United States.

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